The invention relates to a cleaning/washing composition and to an improvement in a method or process of cleaning/washing using such cleaning/washing composition. In particular, the cleaning/washing composition is directed to provide for an enhanced delivery of benefit agents by a system of immiscible liquids with high interfacial tension.
Conventionally fabric is cleaned using water and a detergent surfactant system which is known as wet cleaning. Surfactants adsorb on both fabric and soil and thereby reduce the respective interfacial energies and this facilitates the removal of soil from the fabric. Alternatively it is done by a process called dry cleaning where organic solvents such as perchloroethylene (PCE), petroleum based or Stoddard solvents, chlorofluorocarbon CFC-113 and 1,1,1-trichloroethane are used, all of which are generally aided by a surfactant. The organic solvent helps in the removal of oily soil in the presence of detergents. Soil removal can be achieved by a small reduction in interfacial tension. The particulate soil is largely removed by providing agitation.
It is known that the efficacy of fabric cleaning compositions can be enhanced by adding several benefit agents to the formulations such as fabric softeners, fluorescers, dye transfer inhibitors, optical brighteners etc. However, these pose a problem when formulated along with a surfactant system. Thus, for example, fabric softeners are typically cationic and suffer from instability during storage when associated with anionic detergent actives in formulations. There will also be a problem relating to the viscosity of the formulations when they are associated with ethoxylated nonionic surfactants and this problem will be more pronounced at temperatures higher than 37xc2x0 C.
U.S. Pat. No. 3,640,881 (Hoechst Celanese Corp.) discloses dry cleaning compositions containing an hydrophilic optical brightener and detergent material compatible therewith to simultaneously clean and brighten textile structures and particularly white garments having a significant manmade fiber content. This technology is based in part upon the discovery that in conventional organic dry cleaning systems a water-dispersible optical brightener in the presence of a small volume of water can function as a brightness restorer preventing the textile structures, when being dry cleaned, from dulling, fading, yellowing or acquiring other undesirable characteristics. It is essential to employ a detergent material, especially of the amphoteric type, to enhance the brightening effect.
Our earlier-filed co-pending application WO-A-01/90474, published on Nov. 29, 2001, discloses a process of cleaning fabric using the liquid-liquid interface of at least two immiscible liquid phases with an interfacial tension greater than 5 mN/m, under agitation. It has been demonstrated therein that effective cleaning by this immiscible system can be achieved in the absence of other detergent actives and benefit agents.
The organic solvents used for cleaning are generally toxic and also pose other problems, as they are inflammable and hence create potential fire hazards. Another major concern in solvent cleaning is the tendency of vapour loss from the cleaning system into the atmosphere especially when they are used at elevated temperatures. Solvent cleaning processes generally employ chlorinated solvents that are linked to ozone depletion. Several attempts have been made to avoid these problems and find suitable substitutes.
Regardless of the type of solvent used, which may be water or organic, agitation of garments in the cleaning medium is essential to accelerate the removal of the soluble soil or the insoluble, particulate soil. During dry cleaning when a surfactant is used, a maximum of about 10% of water is also used along with the solvent system in order to facilitate the removal of water soluble stains.
Our copending application 999/MUM/2001, filed on Oct. 12, 2001, teaches a method of cleaning fabric using an immiscible liquid phase in which the less polar solvent has a carbon chain length greater than 6 and/or is a silicone with more than 3 SiO units to circumvent the problem of toxicity, flammability, and environmental impact whilst retaining superior cleaning of fabric.
It has now been found that the efficacy of the benefit agents used in cleaning/washing systems can be improved without encountering the problems in use of conventional surfactant systems, by the use of an immiscible liquid system having an interfacial tension greater than 5 mN/m, wherein the less polar solvent has a carbon chain length of at least 4, and or is a silicone with more than 3 SiO units.
Thus according to an aspect of the present invention there is provided a cleaning/washing composition comprising:
i. an immiscible liquid system with an interfacial tension greater than 5 mN/m, wherein the less polar solvent has a carbon chain length of at least 4 and/or is a silicone with more than 3 SiO units; and
ii. 0.001-20% of one or more benefit agents (as hereinafter more fully described) that is soluble in at least one of the phases.
Preferably the less polar solvent has a carbon chain length, greater than 6. It is particularly preferred that the concentration of the most polar liquid is 10.1-90% (v/v) of the immiscible system and the carbon chain length of the less polar solvent is greater than 12 and more preferably greater than 16.
In accordance with another aspect of the present invention there is provided an improved method of cleaning/washing of fabrics comprising carrying out said step of cleaning/washing under agitation using a cleaning/washing composition comprising:
i. an immiscible liquid system having an interfacial tension greater than 5 mN/m, wherein the less polar solvent has a carbon chain length of at least 4 and/or is a silicone with more than 3 SiO units, and
ii. 0.001-20% of one or more benefit agents that is soluble in at least one of the phases.
Thus according to the essential aspect of the present invention there is provided a fabric cleaning composition comprising an immiscible liquid system having an interfacial tension greater than 5 mN/m and one or more of said benefit agents. The delivery of the benefit agents is enhanced by the use of the immiscible liquid system. Interfacial tension may be measured using various techniques, such as sessile drop, pendant drop, spinning drop, drop volume or Wilhelmy plate method. For the purposes of the present invention, interfacial tension is measured by the Wilhelmy method, using a Kruss Processor Tensiometer K12, at 25xc2x0 C. For some systems, the interfacial tension may change whilst undergoing shearing forces typically encountered in a wash process. It is customary to refer to the interfacial tension under these conditions as a xe2x80x9cdynamic interfacial tensionxe2x80x9d (DIFT) and this may be measured by a maximum bubble pressure technique.
Benefit Agents
The benefit agents may be selected from fluorescers, surfactants, hydrotropes, enzymes, bleaches, dye transfer inhibitors, optical brighteners, fabric softeners, anti redeposition agents, electrolytes, polymers, builders, perfumes, anti-wrinkling agents, easy-ironing agents etc. The level of these agents range between 0.001-20% by weight of the composition. The level of the fluorescers is preferably in the range 0.001-0.5%, dye transfer inhibitors in the range 0.001-1%, fabric softeners 0.001-20% and anti-redeposition agents 0.001 to 1% by weight of the composition.
Solvents
The solvents that can be used in the immiscible liquid system of the invention should be such, that the liquid immiscible system has an interfacial tension of greater than 5 mN/m. The more polar solvents can be selected from water, aromatic solvents, halogenated solvents such as chloromethane, 1,1-dichloroethane, perchloroethylene, carbontetrachloride, 1,1,2-trichloro-1,2,2-trifluoroethane, chlorobenzene, bromobenzene, heterocyclics etc, and alcohols, ethers, esters, and ketones with less than 4 carbon atoms. Preferably the more polar solvent is water. Mixtures of solvents can also be used.
The less polar solvents that have a carbon chain length of at least 4, preferably greater than 6 may be selected from branched and linear alkanes (chemical formula CnH2n+2 where n is at least 4), including but not limited to hexane, heptane, octane, nonane, decane, dodecane, tridecane, tetradecane, pentadecane etc. and mixtures thereof. Commercially available mixtures of this type include Isopar L (C11-C15 alkanes-ex-Exxon) and DF2000 (C11-C15 iso-alkanes; CAS# 90622-58-5, ex-Exxon). They may also be selected from branched and linear alkenes including but not limited to octenes, nonenes, decenes, undecenes, dodecenes etc, with one or more double bonds, and mixtures thereof.
Ethers including fluoroethers such as methoxy nonafluorobutane HFE7100 (i.e. C4F9-OCH3) and ethoxy nonafluorobutane HFE-7200 (i.e. C4F9-OC2H5); esters such as dibutyl phthalate, dioctyl phthalate, C8-C24 saturated and/or unsaturated fatty acid methyl esters, and terpenes, such as limonene, or mixtures of the above may be used. Particularly preferred esters are the C10-C18 fatty acid methyl esters such as methyl laurate, methyl myristate, methyl stearate, methyl linoleate and methyl linolenate and mixtures thereof.
The solvents with more than 3 SiO units may be selected from polydimethyl siloxane oils. Linear and cyclic siloxanes known as Lx and Dx where x is greater than three are suitable examples thereof. Specific examples include
octamethylcyclotetrasiloxane (D4) (ex-Dow Corning),
decamethylcyclopentasiloxane (D5),
dodecamethylcyclohexasiloxane (D6), decamethyltetrasiloxane (L4) and dodecamethyl pentasiloxane (L5).
Agitation
Regardless of the type of solvent used, which may be water or organic, agitation of garments in the cleaning medium is essential to accelerate the removal of the soluble soil or the insoluble, particulate soil. Agitation can be provided by impellers that cover the vertical flow profile or radial flow profile or a combination of both so that thorough mixing of the immiscible liquids take place. Agitation can be provided by impellers that are of the types known as open curved turbine, turbine type propeller, axial flow turbine, flat blade turbine, inverted vane turbine, marine propeller etc. This action may also be accompanied by a tumbling action. Optionally agitation can also be provided by a combination of rotation and tumbling action. Other forms of agitation using gas jets or ultra sound may also be employed. Other forms of agitation generally known in the art can also be employed provided it ensures a good mixing of the immiscible liquid phases.